1. Field of the Invention
The invention relates to a sterilizing apparatus of the type utilized to sterilize hospital and laboratory glassware, liquids, instruments, parenteral solutions, and paper and fabric materials, such as surgical gowns, sheets and pillow cases, and like objects, and to a process for sterilizing such objects.
2. State of the Art
Steam sterilizers are well known and are extensively utilized in hospitals, laboratories and other facilities for the purpose of sterilizing many types of solid, liquid-containing and porous objects. Typical such sterilizers are disclosed in U.S. Pat. Nos. 3,325,042 and 3,488,142.
Steam sterilizers commonly utilize one of two systems to regulate temperature. The system 200 illustrated in FIG. 2 is referred to as a "hi-low" system, utilizing a high-low pressure regulator 214 which has two positions that regulate the pressure, such as at 15 p.s.i.g. (low) or 27 p.s.i.g. (high). These two positions are manually controlled. The low pressure steam is utilized for sterilization at about 250.degree. F. and the high pressure steam is utilized for sterilization at about 270.degree. F. The pressure regulator 214 is manually set for either the low or high pressure and the temperature sensor 218, which is also manually set, then regulates a control valve 216 to open the regulator 214 and introduce more steam to jacket 212 if the temperature deviates from the predetermined temperature to raise the temperature of the sterilizer chamber. The disadvantage of this system is that the operator must make two adjustments (in the temperature sensor 218 and the high-low regulator 214) when going from 250.degree. to 270.degree. F. Failure to do so will result in an unsatisfactory cycle. Also, with this construction, only two predetermined temperatures can be achieved. For example, if a 260.degree. F. cycle is desired, the high-low valve 214 must be set on high and the jacket temperature would reach 270.degree., resulting in superheated steam in the sterilizing chamber.
Another prior art construction 220 is illustrated in FIG. 3. In this construction the low pressure 228 regulator is set, for example, at 15 p.s.i.g. and the high pressure regulator 232 is set, for example, at 35 p.s.i.g. The jacket pressure is established by opening either one of two solenoid valves 226 (for low pressure steam) or 230 (for higher pressure steam). Additional regulators and solenoid valves can be added to give a wider range of pressures and consequent sterilizing temperatures. The temperature sensor 234 regulates the chamber control valve 224, to regulate the introduction of a suitable quantity of steam into the chamber of sterilizer 220, depending upon the predetermined setting and the pressure of the jacket steam. The disadvantages of this apparatus and process are similar to those of the FIG. 2 apparatus in that two selections (rather than one) must be made to establish sterilizer temperature namely, the control valve operating temperature and the particular high pressure or low pressure regulator utilized to supply steam to the sterilizer. Also, this system produces only specific temperatures and cannot be varied to a great variety of temperatures merely by adjusting the temperature controller.
The systems of the prior art are inefficient, in that they require more than a single manual operation in order to achieve a predetermined temperature setting and are therefore more susceptible of error than the apparatus of this invention. The prior art devices are not capable of achieving, with minimal instrumentation, a great variety of temperatures between the temperature established by the low pressure and high pressure supply, and inefficiently use available steam by allowing, at times, the jacket pressure and temperature to be different from the pressure and temperature of the sterilizer interior. The disadvantages of the prior art are overcome by the process and apparatus of this invention.